Portable calculators are well known. Watch and calculator combinations are well known also as shown by U.S. Pat. Nos. 3,928,960 and 3,816,730 issued to Reese and Yamamoto et al respectively each show an electronic calculator with a digital clock showing a common display and operative to function either as a calculator or a clock depending on the state of a switch. A digital alarm clock, stop watch device is known which can store up to 4 alarm times.
U.S. Pat. No. 4,013,901 issued to Williams shows a timekeeping system using integrated injection logic (I.sup.2 L) which has very high density circuity.
U.S. Pat. No. 3,955,355 issued to Luce shows an electronic watch and calculator designed to be worn on the wrist of the user.
As the patents to Luce, Yamamoto, and Reese show there has been no attempt to functionally integrate the clock function with the calculator function utilizing a memory function to produce a record of elapsed time of use of the calculator which might be charged to specific accounts or projects.
Such a function would be very useful to accountants, lawyers, engineers and many others who bill or charge time to others. By using a printout record such a device could be used to replace the traditional time clock mechanism or the manual time record log used in many small companies or firms.
No known device performs the functions of time keeping, calculating, memory and integrate the three to form an electronic stop watch-calculator which keeps a record of the time by account number.